1. Field of the Invention
The present invention relates to a microwave oven, and more particularly, to a microwave oven wherein rigidity of parts for defining an exterior appearance of the microwave oven is improved.
2. Description of the Prior Art
A microwave oven is one of electronic home appliances for kitchen for cooking food using frictional heat between molecules generated while disturbing molecular structures of the food by irradiating microwaves, which serves as a heating source, onto the food. The microwave oven is widely used not only in home but also in restaurants, feeding facilities or the like where a large quantity of food is simultaneously cooked, because of convenience of use for easy heating and cooking of food. A typical example of such a microwave oven is shown in FIG. 1.
Referring to FIG. 1, a cavity assembly 1 functions as a framework of a microwave oven. A cooking chamber 3 in which food is cooked is defined in the cavity assembly 1, and an electronic equipment installation chamber 5 is formed at one side of the cavity assembly 1 in a state where it is partitioned from the cooking chamber 3. A turntable 7 for turning the food thereon is installed in the cooking chamber 3. Parts for generating microwaves, such as a magnetron 9, a high voltage transformer 10 and a capacitor 11, are also installed in the electronic equipment installation chamber 5. Further, a blower fan 12 for cooling the aforementioned parts and generating airflow into/from the cooking chamber 3 is also provided in the electronic equipment installation chamber 5.
A door 13 for causing the cooking chamber 3 to be open and close is fixed and installed to one side of a front face of the cavity assembly 1. The door 13 is hingedly connected to the cavity assembly 1 and provided with a handle 15 at a side of a front surface of the door opposite to the side to which the door is hingedly connected. A control unit 17 for controlling the microwave oven is provided at the other side of the cavity assembly 1.
In general, an outer casing 19, which is made of a metal plate, defines an external appearance of the microwave oven at top and side surfaces thereof. The outer casing 19 is mounted to the cavity assembly 1 so as to enclose the cavity assembly 1 and to shield the electronic equipment installation chamber 5 from the outside.
A back plate 1′ defines a rear face of the cavity assembly 1, more generally, a whole rear surface of the microwave oven.
The microwave oven constructed as such is operated in the following manner. That is, after the door 13 is opened, food to be cooked is put onto the turntable 7 in the cooking chamber 3, and the door 13 is then closed. Thereafter, the control unit 17 is operated to select and begin a desired cooking mode.
However, there are the following problems in the aforementioned conventional microwave oven.
The external appearance of the microwave oven is generally defined by the parts such as the back plate 1′, the door 13 and the outer casing 19. In such a case, the external parts may be damaged by a variety of external forces.
The outer casing 19 is generally formed of a metal plate and defines the top surface and two opposite side surfaces of the microwave oven. Since the surfaces of the microwave oven are planar as a whole, they have weak resistance to the external forces. In particular, in a case where a surface area of the outer casing 19 becomes large as the size of the microwave oven is increased, rigidity of the outer casing 19 is relatively reduced and thus the deformation thereof are frequently produced.
In addition, a clamping means is frequently used to carry the microwave oven. In such a case, a clamping force produced when carrying the microwave oven is transmitted to a packaging box of the microwave oven, and thus, any deformation may be produced at the outer casing 19 or corners of the microwave oven. In order to overcome the problem, a disposable reinforcing material may be used, which results in an increase of costs and inconvenience in handling of the microwave oven.
Further, the microwave oven may inadvertently drop when carrying the microwave oven. At this time, if the microwave oven drops and one of the corners thereof comes into contact with the ground, impact load applied to the microwave oven is concentrated on the corner which in turn may be greatly deformed.
In addition, the back plate 1′ defines the external appearance of the microwave oven as well as a rear face of the cavity assembly 1. The back plate 1′ has a problem in that either border regions excluding portions to be welded for constituting the cavity assembly 1 or regions adjacent to a hole through which a power cable is drawn to the outside are relatively weak in view of their rigidity.
Finally, the door 13 also defines the external appearance of the microwave oven, and a force for opening the door 13 may cause the microwave oven to be deformed. That is, the handle 15 should be pulled outwards so as to open the door 13. However, since the door 13 is in a state where it is locked or fastened to the cavity assembly 1 with a latch (not shown), the door 13 cannot be opened until a force enough to overcome the locking force of the latch is applied thereto.
Therefore, the force exerted on the handle for opening the door 13 causes the door to be deformed or twisted, and consequently, a gap may be generated between a rear surface of the door 13 and the front face of the cavity assembly 1 due to repeated use of the door. Electromagnetic waves leak from the interior of the cooking chamber 3 through the gap, thereby exerting a bad influence on a user and causing cooking time to be lengthened.